One common feature of all the previous generations of wireless communications up to 5G is the assumption that wireless channel is truly random and hence cannot be controlled. Thus the various mechanisms (e.g., MIMO, orthogonal frequency-division multiplexing (OFDM), etc.) developed for the performance improvement of wireless communication systems over the years considered wireless channel impairments as unavoidable and tried to mitigate the adverse effects of wireless channel at the transmitter and receiver. Recently, a new technique called the IRS, which uses artificial materials to control the propagation characteristics of the radio environment, is being seen a revolutionary technology to enhance the performance of future wireless systems [1]}, [2]}, [3]}. Instead of compensating the destructive effects of propagation environment at receiver and transmitter, IRS allows the radio environments to reconfigure itself in such a way that the negative effects of the environment are undone before it reaches the receiver. The ability to control wireless channel brings a true paradigm shift in the fundamentals of design and deployment of wireless communication systems since the interaction of radio signal with the radio environment can be deterministically defined to a large extent.
